An NMR probe holds a sample placed in a uniform polarizing magnetic field in NMR spectrometry. A coil is disposed close to the sample within the probe to apply an exciting RF magnetic field to the sample. The resultant resonance signal of the sample is picked up by the coil and delivered to a receiver circuit. The receiver circuit generates an output signal. A computer takes the Fourier transform of the signal to obtain an NMR spectrum.
The NMR apparatus is most often characterized in gross by cylindrical symmetry. The internal structure of the probe generally exhibits no geometric symmetry because it contains circuits, circuit elements, connectors, fluid supply tubes, and mechanical mounting means for all of the above and the like. A typical NMR magnet is of the superconducting variety and is housed in a dewar which includes a room temperature cylindrical bore in which a very carefully controlled homogeneous magnetic field is sustained by operation of the superconducting magnet in the interior of the dewar. The NMR probe contains the excitation and detection interface to the sample and is mounted in a cylindrical housing for insertion in the bore.
It is often desirable to use an NMR probe to resonate at frequencies outside of the standard range of frequencies of the probe. In addition, NMR probes are used in single tune mode and double tune mode. Because existing NMR probes are generally constructed for use only in either single tune operation or double tune operation, two NMR probes are needed for applications in single tune and double tune.